U.S. patent number RE45,845 [Application Number 14/305,687] was granted by the patent office on 2016-01-19 for cutting tool and round double sided cutting insert therefor.
This patent grant is currently assigned to ISCAR, LTD.. The grantee listed for this patent is Iscar, Ltd.. Invention is credited to Yuri Men, Amir Satran.
United States Patent |
RE45,845 |
Men , et al. |
January 19, 2016 |
Cutting tool and round double sided cutting insert therefor
Abstract
A cutting insert for retention in a rotating cutting tool having
an axis of rotation has two opposing end surfaces and a peripheral
surface extending therebetween, each end surface having a mutual
first axis of symmetry passing through the end surfaces about which
each end surface has N-fold rotational symmetry for some value of N
where N is chosen from the group consisting of 2, 3 and 4. A
peripheral cutting edge is formed at the junction between each end
surface and the peripheral surface, the peripheral cutting edge
having N curved cutting edges merging with N straight cutting edges
which extend between the curved cutting edges at extremities
thereof. The curved cutting edges of the two end surfaces are not
aligned in an end view of the cutting insert along the first axis
of symmetry.
Inventors: |
Men; Yuri (Haifa,
IL), Satran; Amir (Kfar Vradim, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Iscar, Ltd. |
Tefen |
N/A |
IL |
|
|
Assignee: |
ISCAR, LTD. (Tefen,
IL)
|
Family
ID: |
41346094 |
Appl.
No.: |
14/305,687 |
Filed: |
June 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
12507843 |
Jul 23, 2009 |
8206066 |
Jun 26, 2012 |
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Foreign Application Priority Data
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23B
27/16 (20130101); B23C 5/2213 (20130101); B23C
5/207 (20130101); B23C 5/202 (20130101); B23C
5/2221 (20130101); B23C 5/20 (20130101); B23C
2200/201 (20130101); B23C 2210/168 (20130101); B23C
2200/203 (20130101); Y10T 407/23 (20150115); B23C
2200/128 (20130101); Y10T 407/1924 (20150115) |
Current International
Class: |
B23B
27/16 (20060101); B23C 5/20 (20060101); B23C
5/22 (20060101) |
Field of
Search: |
;407/113,42 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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20020271 |
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Jan 2002 |
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DE |
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102005043842 |
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Mar 2007 |
|
DE |
|
0054481 |
|
Jun 1982 |
|
EP |
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0300247 |
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Jan 1989 |
|
EP |
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0574376 |
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Dec 1993 |
|
EP |
|
0925863 |
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Jun 1999 |
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EP |
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H10-263916 |
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Oct 1998 |
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JP |
|
2008-018515 |
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Jan 2008 |
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JP |
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2004/002664 |
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Jan 2004 |
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WO |
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WO 2004/094092 |
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Nov 2004 |
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WO |
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Other References
Extended search report dated Mar. 11, 2015 issued in European
counterpart application (No. 14199208.1). cited by applicant .
International Search Report, PCT/IL2009/000814, dated Dec. 21,
2009. cited by applicant .
International Preliminary Report on Patentability in counterpart
international application No. PCT/IL2009/000814, completed Mar. 12,
2010. cited by applicant.
|
Primary Examiner: Clarke; Sara
Attorney, Agent or Firm: Womble Carlyle Sandridge & Rice
PLLC
Claims
What is claimed is:
1. A double-sided cutting insert (18, 118) for retention in a
rotating cutting tool having an axis of rotation, the cutting
insert comprising: two opposing end surfaces (28, 128) and a
peripheral surface (26) extending therebetween, each end surface
having a mutual first axis of symmetry (B) passing through the end
surfaces about which each end surface has N-fold rotational
symmetry, where N is a number from the group consisting of 2, 3 and
4; a peripheral cutting edge (66, 166) formed at the junction
between each end surface and the peripheral surface, the peripheral
cutting edge comprising N curved cutting edges (32, 34; 132, 134)
merging with N straight cutting edges (44, 50; 144, 150) which
extend between the curved cutting edges at extremities thereof;
wherein: the curved cutting edges of the two end surfaces are not
aligned, as seen in an end view of the cutting insert: and each of
the N curved cutting edges (32, 34; 132, 134) lies on a torus and
extends along an angle equal to or larger than 120.degree., as seen
along the first axis of symmetry (B).
2. The cutting insert (18, 118) according to claim 1, wherein: N
cutting edge pivot axes (C), located in a mid portion (35) of each
of the N curved cutting edges, extend parallel to the first axis of
symmetry (B), and each of the N curved cutting edges (32, 34; 132,
134) of one of the end surfaces (28, 128) is rotated about its
associated cutting edge pivot axis (C) relative to an opposite
curved cutting edge (34', 32') of the other end surface, as seen in
an end view of the cutting insert.
3. A double-sided cutting insert (18, 118) for retention in a
rotating cutting tool having an axis of rotation, the cutting
insert comprising: two opposing end surfaces (28, 128) and a
peripheral surface (26) extending therebetween, each end surface
having a mutual first axis of symmetry (B) passing through the end
surfaces about which each end surface has N-fold rotational
symmetry, where N is a number from the group consisting of 2, 3 and
4; a peripheral cutting edge (66, 166) formed at the junction
between each end surface and the peripheral surface, the peripheral
cutting edge comprising N curved cutting edges (32, 34; 132, 134)
merging with N straight cutting edges (44, 50; 144, 150) which
extend between the curved cutting edges at extremities thereof;
wherein: the curved cutting edges of the two end surfaces are not
aligned, as seen in an end view of the cutting insert; the two end
surfaces (28, 128) are identical; a major angular portion (MP11,
MP12) of each of the curved cutting edges extends along an angle
equal to or larger than 120.degree. as seen in an end view of the
cutting insert.
4. The cutting insert (118) according to claim 1, wherein: one
extremity (136, 140) of any given curved cutting edge (132, 134) is
located further from a median plane (M) of the cutting insert than
the other extremity (138, 142) of the given curved cutting edge,
the median plane being located midway between the end surfaces.
5. A double-sided cutting insert (18, 118) for retention in a
rotating cutting tool having an axis of rotation, the cutting
insert comprising: two opposing end surfaces (28, 128) and a
peripheral surface (26) extending therebetween, each end surface
having a mutual first axis of symmetry (B) passing through the end
surfaces about which each end surface has N-fold rotational
symmetry, where N is a number from the group consisting of 2, 3 and
4; a peripheral cutting edge (66, 166) formed at the junction
between each end surface and the peripheral surface, the peripheral
cutting edge comprising N curved cutting edges (32, 34; 132, 134)
merging with N straight cutting edges (44, 50; 144, 150) which
extend between the curved cutting edges at extremities thereof;
wherein: the curved cutting edges of the two end surfaces are not
aligned, as seen in an end view of the cutting insert; and each of
the N curved cutting edges (32, 34; 132, 134) extends along an
angle equal to or larger than 120.degree., as seen along the first
axis of symmetry (B).
6. The cutting insert (18) according to claim 1, wherein: the
curved cutting edges (32, 34) associated with one of the end
surfaces (28) are located in a first reference plane (P1) and the
curved cutting edges (32', 34') associated with the other end
surface are located in a second reference plane (P2), the first and
second reference planes being parallel to each other and located
equidistant from and on either side of a median plane (M) of the
cutting insert, the median plane being located midway between the
end surfaces.
7. The cutting insert (18, 118) according to claim 1, wherein: the
two end surfaces (28, 128) are identical.
8. The cutting insert according to claim 7, wherein: a major
angular portion (MP11, MP12) of each of the curved cutting edges
extends along an angle equal to or larger than 120.degree. as seen
in an end view of the cutting insert.
9. The cutting insert (18, 118) according to claim 8, wherein: the
first main cutting edge (32, 132) and the second main cutting edge
(34, 134) follow a major first radius of curvature (MR11, MR12)
along the major angular portion (MP11, MP12) thereof and a minor
second radius of curvature (MR21, MR22) along a minor angular
portion (MP21, MP22) thereof.
10. A double-sided cutting insert (18, 118) for retention in a
rotating cutting tool having an axis of rotation, the cutting
insert comprising: two opposing end surfaces (28, 128) and a
peripheral surface (26) extending therebetween, each end surface
having a mutual first axis of symmetry (B) passing through the end
surfaces about which each end surface has N-fold rotational
symmetry, where N is a number from the group consisting of .[.2, 3
and 4.]. .Iadd.2 and 4.Iaddend.; a peripheral cutting edge (66,
166) formed at the junction between each end surface and the
peripheral surface, the peripheral cutting edge comprising N curved
cutting edges (32, 34; 132, 134) merging with N straight cutting
edges (44, 50; 144, 150) which extend between the curved cutting
edges at extremities thereof; wherein: the curved cutting edges of
the two end surfaces are not aligned, as seen in an end view of the
cutting insert; the cutting insert comprises a through bore (30),
having a through bore axis (B) constituting the first axis of
symmetry, that extends between the two end surfaces (28); and the
peripheral surface (26) comprises first (58), second (60), third
(62) and fourth (64) pairs of side abutment surfaces, each pair of
side abutment surfaces having 180.degree. rotational symmetry
around the through bore axis (B).
11. The cutting insert according to claim 10, wherein: a first end
surface of the two opposing end surfaces (28, 128) constituting an
upper surface (22, 122) defining a first reference plane (P1), a
second end surface of the two opposing end surfaces constituting a
lower surface (24, 124) defining a second reference plane (P2)
parallel to the first reference plane; the curved cutting edges
comprise a first main cutting edge (32, 132) and a second main
cutting edge (34, 134); in an end view of the cutting insert the
first main cutting edge (32, 132) has a first radius of curvature
(R1) with respect to a first cutting edge axis (A1) and the second
main cutting edge (34, 134) has a second radius of curvature (R2)
with respect to a second cutting edge axis (A2), the first cutting
edge axis (A1) and the second cutting edge axis (A2) are parallel
to the through bore axis (B) and located at opposite sides thereof;
the first cutting edge axis (A1) is located a first distance (D1)
from the second main cutting edge (34, 134), the through bore axis
(B) is located a second distance (D2) from the second main cutting
edge (34, 134), and the first distance (D1) is smaller than the
second distance (D2).
12. The cutting insert (18, 118) according to claim 11, wherein:
the cutting insert has 180.degree. rotational symmetry around a
second symmetry axis (S), the second symmetry axis lies on a median
plane (M) between the first and the second reference planes (P1,
P2), and intersects the peripheral surface (26) at two median
insert symmetry points (56); each of the median insert symmetry
points is formed at the intersection of a first reference line (L1)
with a second reference line (L2), as seen in a first side view of
the cutting insert that is perpendicular to a given secondary
cutting edge; the first reference line (L1) connects the leading
end (36, 136) of a first main cutting edge (32, 132) of a given end
surface (28, 128) with the leading end (36, 136) of a first main
cutting edge (32, 132) of an opposite end surface (28, 128); and
the second reference line (L2) connects the trailing end (42, 142)
of a second main cutting edge (34, 134) of a given end surface (28)
with the trailing end (42, 142) of a second main cutting edge (34,
134) of an opposite end surface (28).
13. The cutting insert (18, 118) according to claim 12, wherein the
first cutting edge axis (A1) and the second cutting edge axis (A2)
are located at opposite sides of an imaginary plane (N) that is
perpendicular to a symmetry plane (SP) that contains the first axis
of symmetry (B) and the second symmetry axis (S).
14. The cutting insert (18,118) according to claim 13, wherein:
each side abutment surface of the first pair of side abutment
surfaces (58) converges towards each other in a direction toward
the upper surface (22, 122); each side abutment surface of the
second pair of side abutment surfaces (60) converges towards each
other in a direction toward the lower surface (24, 124); each side
abutment surface of the third pair of side abutment surfaces (62)
converges towards each other in a direction toward the upper
surface (22, 122); and each side abutment surface of the fourth
pair of side abutment surfaces (64) converges towards each other in
a direction toward the lower surface (24, 124).
15. The cutting insert (18, 118) according to claim 14, wherein:
the third pair of side abutment surfaces (62) has 180.degree.
rotational symmetry with the fourth pair of side abutment surfaces
(64) around the symmetry axis (S).
16. The cutting insert (18, 118) according to claim 15, wherein:
the first pair of side abutment surfaces (58) converge towards each
other in a direction toward the upper surface (22, 122) as viewed
in a cross-section taken in a first section plane (P3), the first
section plane contains the through bore axis (B) and is obliquely
disposed, as seen in an end view of the cutting insert, with
respect to a symmetry plane (SP) containing the through bore axis
(B) and the symmetry axis (S).
17. The cutting insert (18, 118) according to claim 16, wherein:
the second pair of side abutment surfaces (60) converge towards
each other in a direction toward the lower surface (24, 124) as
viewed in a cross-section taken in a second section plane (P4), the
second section plane (P4) contains the through bore axis (B) and is
obliquely disposed at a plane angle (.phi.), as seen in a top view
of the cutting insert, with respect to the symmetry plane (SP) and
with respect to the first section plane (P3).
18. The cutting insert (18, 118) according to claim 17, wherein:
the plane angle (.phi.) is 80.degree..
19. The cutting insert (18, 118) according to claim 17, wherein:
the peripheral surface (26) forms with the first reference plane
(P1) and with the second reference plane (P2) an obtuse first
internal included angle (.alpha.), as seen in a first side view of
the cutting insert that is perpendicular to a secondary cutting
edge (44, 50, 144, 150); and the peripheral surface (26) forms with
the first reference plane (P1) and with the second reference plane
(P2) an acute second internal included angle (.beta.), as seen in a
second side view of the cutting insert that is perpendicular to the
first side view.
20. A cutting insert (218) for retention in a rotating cutting tool
(10) having an axis of rotation (A), the cutting insert comprising:
two opposing end surfaces (228) and a peripheral surface (226)
extending therebetween, each end surface having a mutual first axis
of symmetry (B) passing through the end surfaces about which each
end surface has 180.degree. rotational symmetry; a peripheral
cutting edge (266) formed at the junction between a first end
surface, constituting an upper surface (222), and the peripheral
surface, the peripheral cutting edge comprising two curved cutting
edges (232, 234) merging with two straight cutting edges which
extend between the curved cutting edges at extremities thereof; a
continuously extending rake surface (268) extends inwardly from the
peripheral cutting edge, the rake surface is slanted at a rake
slant angle (.lamda.) with respect to a second end surface,
constituting a lower surface (224); the upper surface comprises a
rake inner extremity (92) at the innermost extremity of the rake
surface and a bore upper end (96) at the uppermost end of a through
bore (30) that extends between the end surfaces, a length between a
given point (98) on the peripheral cutting edge and the rake inner
extremity comprises a first rake length (H1) and a length between
the given point and the bore upper end comprises a second rake
length (H2), the first rake length and the second rake length taken
in a plane parallel to the lower surface; wherein: the rake slant
angle is equal to or greater than 25.degree.; a rake extension
ratio (E), defined as a ratio between the first rake length (H1)
and the second rake length (H2), is smaller than 1 and equal to or
greater than 0.8; and a major angular portion (MP11, MP12) of each
of the curved cutting edges lies on a torus and extends along an
angle equal to or larger than 120.degree. as seen along the first
axis of symmetry (B).
21. The cutting insert (218) according to claim 20, wherein the
peripheral surface comprises: a first (258) pair of side abutment
surfaces that converge towards each other in a direction toward the
upper surface; and a third (262) pair of side abutment surfaces
that converge towards each other in a direction toward the upper
surface.
22. A cutting tool (10) having a longitudinal axis of rotation (A)
and comprising: a tool body (12) having at least one insert pocket
(14) formed in a front end (16) of the tool body and a cutting
insert (18, 118) retained in the at least one insert pocket,
wherein: the at least one insert pocket comprises: a pocket base
abutment surface (74); a threaded bore (76) extending tangentially
rearwardly from the pocket base abutment surface; pocket side walls
(78) extending upwardly from the pocket base abutment surface and
comprising a first pocket abutment surface (80) forming an acute
first pocket internal angle (.gamma.) with the pocket base abutment
surface, and a second pocket abutment surface (82) forming an acute
second pocket internal angle (.delta.) with the pocket base
abutment surface, the first and second pocket abutment surfaces
being spaced apart from one another; and the cutting insert (18,
118) comprises: two opposing end surfaces (28, 128) and a
peripheral surface (26) extending therebetween, each end surface
having a mutual first axis of symmetry (B) passing through the end
surfaces about which each end surface has N-fold rotational
symmetry for some value of N where N is a number from the group
consisting of 2, 3 and 4; a peripheral cutting edge (66, 166)
formed at the junction between each end surface and the peripheral
surface, the peripheral cutting edge comprising N curved cutting
edges (32, 34; 132, 134) merging with N straight cutting edges (44,
50; 144, 150) which extend between the curved cutting edges at
extremities thereof, wherein the curved cutting edges of the two
end surfaces are not aligned, as seen in an end view of the cutting
insert.
23. The cutting tool according to claim 22, wherein: the cutting
insert further comprises first (58), second (60), third (62) and
fourth (64) pairs of side abutment surfaces, each pair of the side
abutment surfaces having 180.degree. rotational symmetry around the
through bore axis (B), wherein: the first pair of side abutment
surfaces (58) converge towards each other in a direction toward the
upper surface (22, 122), the second pair of side abutment surfaces
(60) converge towards each other in a direction toward the lower
surface (24, 124), the third pair of side abutment surfaces (62)
converge towards each other in a direction toward the upper surface
(22, 122), the fourth pair of side abutment surfaces (64) converge
towards each other in a direction toward the lower surface (24,
124), the third pair has 180.degree. rotational symmetry with the
fourth pair around a second symmetry axis (S) that passes between
the third pair and the fourth pair, the upper surface defines a
first reference plane (P1) and the lower surface defines a second
reference plane (P2), the first and second reference planes are
parallel to a median plane (M) that is located midway between the
upper surface and the lower surface; the peripheral surface (26)
forms with the first reference plane (P1) and with the second
reference plane (P2) an obtuse first internal included angle (a),
as seen in a first side view of the cutting insert that is
perpendicular to a given secondary cutting edge; the peripheral
surface (26) forms with the first reference plane (P1) and with the
second reference plane (P2) an acute second internal included angle
(.beta.), as seen in a second side view of the cutting insert that
is perpendicular to the first side view: the upper surface (22,
122) is provided with a planar upper central abutment surface (70,
170), constituting an insert upper base abutment surface, that
extends inwardly from an associated rake surface (68, 168) toward
the through bore (30); and the lower surface (24, 124) is provided
with a planar lower central abutment surface (72), constituting an
insert lower base abutment surface, that extends inwardly from the
associated rake surface (68, 168) toward the through bore (30);
wherein, in a retained position of the cutting insert (18, 118):
the insert lower base abutment surface (72) abuts the pocket base
abutment surface (74); one abutment surface of the insert first
pair of side abutment surfaces (58) abuts the first pocket abutment
surface (80); one abutment surface of the insert third pair of side
abutment surfaces (62) abuts the second pocket abutment surface
(82); and a clamping screw (20) passes through the through bore
(30) of the cutting insert and threadingly engages the threaded
bore (76) of the insert pocket.
24. The cutting tool (10) according to claim 23, wherein: the at
least one insert pocket (14) is provided with a pocket abutment
relief surface (84) that is located above the second pocket
abutment surface (82), the pocket abutment relief surface being
relieved from the adjacent abutment surface of the insert fourth
pair of side abutment surfaces (64) in a retained position of the
cutting insert.
25. The cutting tool (10) according to claim 22, wherein: the
cutting insert (18, 118) is four times indexable within the at
least one insert pocket (14).
26. The cutting tool (10) according to claim 22, wherein: the first
pocket abutment surface (80) forms with the second pocket abutment
surface (82) an acute pocket angle (.theta.) as seen in a top view
of the at least one insert pocket (14).
27. The cutting tool (10) according to claim 22, wherein: the at
least one insert pocket (14) is provided with a pocket relief
channel (86) located between the pocket side walls (78) and the
pocket base abutment surface (74).
.Iadd.28. A double-sided cutting insert for retention in a rotating
cutting tool having an axis of rotation, the cutting insert
comprising: two opposing end surfaces and a peripheral surface
extending therebetween, each end surface having a mutual first axis
of symmetry (B) passing through the end surfaces about which each
end surface has N-fold rotational symmetry, where N is a number
from the group consisting of 2 and 4; a peripheral cutting edge
formed at the junction between each end surface and the peripheral
surface, the peripheral cutting edge comprising N curved cutting
edges merging with N straight cutting edges which extend between
the curved cutting edges at extremities thereof; wherein: the
curved cutting edges of the two end surfaces are not aligned, in a
direction along the first axis of symmetry (B); the cutting insert
comprises a through bore, having a through bore axis (B)
constituting the first axis of symmetry, that extends between the
two end surfaces; and the peripheral surface comprises first,
second, third and fourth pairs of side abutment surfaces, each pair
of side abutment surfaces having 180.degree. rotational symmetry
around the through bore axis (B). .Iaddend.
.Iadd.29. The cutting insert according to claim 28, wherein: in a
top view of the cutting insert, the curved cutting edges are longer
than the straight cutting edges. .Iaddend.
.Iadd.30. The cutting insert according to claim 29, wherein: N=4
and the cutting insert has eight curved cutting edges.
.Iaddend.
.Iadd.31. The cutting insert according to claim 29, wherein: one
extremity of any given curved cutting edge is located further from
a median plane of the cutting insert than the other extremity of
the given curved cutting edge, the median plane being located
midway between the end surfaces. .Iaddend.
.Iadd.32. The cutting insert according to claim 31, wherein: the
curved cutting edges associated with one of the end surfaces define
a first reference plane and the curved cutting edges associated
with the other end surface define a second reference plane, with
the entire cutting insert being located between the first reference
plane and the second reference plane; and the first and second
reference planes are parallel to each other and located equidistant
from and on either side of the median plane of the cutting insert.
.Iaddend.
.Iadd.33. The cutting insert according to claim 32, wherein: at
each end surface, the N curved cutting edges and the N straight
cutting edges form a continuously extending peripheral cutting edge
that is associated with a rake surface that extends continuously
along the entire circumference of that end surface; the rake
surface merges with a central abutment surface; and the entire
central abutment surface is located closer to the median plane than
the reference plane associated with that end surface. .Iaddend.
.Iadd.34. The cutting insert according to claim 33, wherein: at
said each end surface, the rake surface merges with the upper
central abutment surface through an undercut. .Iaddend.
.Iadd.35. The cutting insert according to claim 32, wherein: the
cutting insert has 180.degree. rotational symmetry around a second
symmetry axis (S), the second symmetry axis lies on the median
plane between the first and the second reference planes and
intersects the peripheral surface at two median insert symmetry
points. .Iaddend.
.Iadd.36. The cutting insert according to claim 29, wherein: the
curved cutting edges associated with one of the end surfaces are
located in a first reference plane and the curved cutting edges
associated with the other end surface are located in a second
reference plane, with the entire cutting insert being located
between the first reference plane and the second reference plane;
and the first and second reference planes are parallel to each
other and located equidistant from and on either side of a median
plane of the cutting insert, the median plane being located midway
between the end surfaces. .Iaddend.
.Iadd.37. The cutting insert according to claim 36, wherein: at
each end surface, the N curved cutting edges and the N straight
cutting edges form a continuously extending peripheral cutting edge
that is associated with a rake surface that extends continuously
along the entire circumference of that end surface; the rake
surface merges with a central abutment surface; and the entire
central abutment surface is located closer to the median plane than
the reference plane associated with that end surface. .Iaddend.
.Iadd.38. The cutting insert according to claim 37, wherein: at
said each end surface, the rake surface merges with the upper
central abutment surface through an undercut. .Iaddend.
.Iadd.39. The cutting insert according to claim 36, wherein: the
cutting insert has 180.degree. rotational symmetry around a second
symmetry axis (S), the second symmetry axis lies on the median
plane between the first and the second reference planes and
intersects the peripheral surface at two median insert symmetry
points. .Iaddend.
.Iadd.40. A cutting tool having a longitudinal axis of rotation (A)
and comprising: a tool body having at least one insert pocket
formed in a front end of the tool body and a cutting insert in
accordance with claim 28 retained in the at least one insert
pocket, wherein: the at least one insert pocket comprises: a pocket
base abutment surface; and a threaded bore extending tangentially
rearwardly from the pocket base abutment surface. .Iaddend.
.Iadd.41. The cutting insert according to claim 28, wherein: a
section plane containing the through bore axis (B) and any point on
any one of the straight cutting edges intersects an adjacent side
abutment surface which slopes inwardly with respect to the through
bore axis (B), in an axial direction away from an associated end
surface and towards the opposite end surface. .Iaddend.
.Iadd.42. A double-sided cutting insert for retention in a rotating
cutting tool having an axis of rotation, the cutting insert
comprising: two opposing end surfaces and a peripheral surface
extending therebetween, each end surface having a mutual first axis
of symmetry (B) passing through the end surfaces about which each
end surface has N-fold rotational symmetry, where N is a number
from the group consisting of 2 and 4; a peripheral cutting edge
formed at the junction between each end surface and the peripheral
surface, the peripheral cutting edge comprising N curved cutting
edges merging with N straight cutting edges which extend between
the curved cutting edges at extremities thereof; wherein: in a top
view of the cutting insert, the curved cutting edges are longer
than the straight cutting edges; a median plane of the cutting
insert is located midway between the end surfaces; one extremity of
any given curved cutting edge is located further from the median
plane than the other extremity of the given curved cutting edge;
the cutting insert comprises a through bore, having a through bore
axis (B) constituting the first axis of symmetry, that extends
between the two end surfaces; and the peripheral surface comprises
first, second, third and fourth pairs of side abutment surfaces,
each pair of side abutment surfaces having 180.degree. rotational
symmetry around the through bore axis (B). .Iaddend.
.Iadd.43. The cutting insert according to claim 42, wherein: N=4
and the cutting insert has eight curved cutting edges.
.Iaddend.
.Iadd.44. The cutting insert according to claim 42, wherein: the
curved cutting edges associated with one of the end surfaces define
a first reference plane and the curved cutting edges associated
with the other end surface define a second reference plane, with
the entire cutting insert being located between the first reference
plane and the second reference plane; and the first and second
reference planes are parallel to each other and located equidistant
from and on either side of the median plane of the cutting insert.
.Iaddend.
.Iadd.45. The cutting insert according to claim 44, wherein: at
each end surface, the N curved cutting edges and the N straight
cutting edges form a continuously extending peripheral cutting edge
that is associated with a rake surface that extends continuously
along the entire circumference of that end surface; the rake
surface merges with a central abutment surface; and the entire
central abutment surface is located closer to the median plane than
the reference plane associated with that end surface. .Iaddend.
.Iadd.46. The cutting insert according to claim 45, wherein: at
said each end surface, the rake surface merges with the upper
central abutment surface through an undercut. .Iaddend.
.Iadd.47. The cutting insert according to claim 42, wherein: the
cutting insert has 180.degree. rotational symmetry around a second
symmetry axis (S), the second symmetry axis lies on the median
plane between the first and the second reference planes and
intersects the peripheral surface at two median insert symmetry
points. .Iaddend.
.Iadd.48. The cutting insert according to claim 42, wherein: a
section plane containing the through bore axis (B) and any point on
any one of the straight cutting edges intersects an adjacent side
abutment surface which slopes inwardly with respect to the through
bore axis (B), in an axial direction away from an associated end
surface and towards the opposite end surface. .Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to a milling cutting insert having
rounded cutting edges and particularly to a double-sided cutting
insert of such a kind.
BACKGROUND OF THE INVENTION
When producing turbine blades, the final machining stage of the
internal surface of the turbine blade is typically done by means of
milling cutting inserts having round cutting edges. In such a case,
the total usable sector used to cut by such a cutting insert is
usually greater than 120.degree., therefore, the cutting insert may
be indexed only two times since a third indexing would not be able
to utilize a full range sector, i.e., a cutting edge spanning more
than 120.degree..
Known round cutting inserts or cutting inserts having round cutting
edges are often single sided, and, as mentioned, may fully utilize
only two cutting edges. For example, U.S. Pat. No. 4,175,896
discloses a single sided cutting insert having two arcuate cutting
edges which are eccentric to each other and separated from each
other by diametrically symmetric flat faces.
Round double sided cutting inserts are typically ceramic inserts
and are devoid of a central through bore for the passage of a
clamping screw. The lack of a through bore is a disadvantage since
it requires utilizing a more complex and expensive retaining
system.
It is an object of the present invention to provide a double-sided
indexable cutting insert having four or more round cutting
edges.
It is an object of the present invention to provide a double-sided
indexable cutting insert having four round cutting edges wherein
each of the cutting edges extends more than 120.degree..
It is an object of the present invention to provide a tool holder
for a double sided cutting insert having four rounded cutting edges
and a through bore, the cutting insert being retained within the
tool holder by means of a clamping screw that passes through the
through bore.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a
cutting insert for retention in a rotating cutting tool having an
axis of rotation, the cutting insert comprising: two opposing end
surfaces and a peripheral surface extending therebetween, each end
surface having a mutual first axis of symmetry passing through the
end surfaces about which each end surface has N-fold rotational
symmetry for some value of N where N is chosen from the group of 2,
3 and 4; a peripheral cutting edge formed at the junction between
each end surface and the peripheral surface, the peripheral cutting
edge comprising N curved cutting edges merging with N straight
cutting edges which extend between the curved cutting edges at
extremities thereof; wherein: the curved cutting edges of the two
end surfaces are not aligned in an end view of the cutting insert
along the first axis of symmetry.
Typically, N cutting edge axes, located in a mid portion of each of
the N curved cutting edges, extend parallel to the first axis of
symmetry, and each of the N curved cutting edges of one of the end
surfaces is rotated about its associated cutting edge pivot axis
relative to an opposite curved cutting edge of the other end
surface, as seen in an end view of the cutting insert along the
first axis of symmetry.
Advantageously, each of the N curved cutting edges lies on a
torus.
Further advantageously, each operative curved cutting edge sweeps
out a portion of a torus when the cutting insert is retained in the
rotating cutting tool and the rotating cutting tool is rotated
about its axis of rotation by 360.degree..
In one embodiment, one extremity of any given curved cutting edge
is located further from a median plane of the cutting insert than
the other extremity of the given curved cutting edge, the median
plane being located midway between the end surfaces.
In one embodiment, the curved cutting edges associated with one of
the end surfaces are located in a first reference plane and the
curved cutting edges associated with the other end surface are
located in a second reference plane, the first and second reference
planes being parallel to each other and located equidistant from
and on either side of a median plane of the cutting insert, the
median plane being located midway between the end surfaces.
Typically, the cutting insert comprises a through bore, having a
through bore axis constituting the first axis of symmetry, that
extends between the two end surfaces; and the peripheral surface
comprises a first, second, third and fourth pairs of side abutment
surfaces, each pair of side abutment surfaces has 180.degree.
rotational symmetry around the through bore axis.
In one embodiment, the two end surfaces are identical.
If desired, a major portion of each of the curved cutting edges
extends along an angle equal to or larger than 120.degree. as seen
along the first axis of symmetry.
In one embodiment, a first end surface of the two opposing end
surfaces constituting an upper surface defining a first reference
plane, a second end surface of the two opposing end surfaces
constituting a lower surface defining a second reference plane
parallel to the first reference plane; the curved cutting edges
comprise a first main cutting edge and a second main cutting edge;
in an end view of the cutting insert the first main cutting edge
has a first radius of curvature with respect to a first cutting
edge axis and the second main cutting edge has a second radius of
curvature with respect to a second cutting edge axis, the first
cutting edge axis and the second cutting edge axis are parallel to
the through bore axis and located at opposite sides thereof; the
first cutting edge axis is located a first distance from the second
main cutting edge, the through bore axis is located a second
distance from the second main cutting edge, and the first distance
is smaller than the second distance.
Typically, the cutting insert has 180.degree. rotational symmetry
around a second symmetry axis, the second symmetry axis lies on a
median plane between the first and the second reference planes, and
intersects the peripheral surface at two median insert symmetry
points; each of the median insert symmetry points is formed at the
intersection of a first reference line with a second reference
line, as seen in a first side view of the cutting insert that is
perpendicular to a given secondary cutting edge; the first
reference line connects the leading end of a first main cutting
edge of a given end surface with the leading end of a first main
cutting edge of an opposite end surface; and the second reference
line connects the trailing end of a second main cutting edge of a
given end surface with the trailing end of a second main cutting
edge of an opposite end surface.
In one embodiment, the first cutting edge axis and the second
cutting edge axis are located at opposite sides of an imaginary
plane that is perpendicular to a symmetry plane that contains the
first axis of symmetry and the second symmetry axis.
Further in accordance with the present invention there is provided
a cutting insert for retention in a rotating cutting tool having an
axis of rotation, the cutting insert comprising: two opposing end
surfaces and a peripheral surface extending therebetween, each end
surface having a mutual first axis of symmetry passing through the
end surfaces about which each end surface has 180.degree.
rotational symmetry; a peripheral cutting edge formed at the
junction between a first end surface, constituting an upper
surface, and the peripheral surface, the peripheral cutting edge
comprising two curved cutting edges merging with two straight
cutting edges which extend between the curved cutting edges at
extremities thereof; a continuously extending rake surface extends
inwardly from the peripheral cutting edge, the rake surface is
slanted at a rake slant angle with respect to a second end surface,
constituting a lower surface; the upper surface comprises a rake
inner extremity at the innermost extremity of the rake surface and
a bore upper end at the uppermost end of a through bore that
extends between the end surfaces, a length between a given point on
the peripheral cutting edge and the rake inner extremity comprises
a first rake length and a length between the given point and the
bore upper end comprises a second rake length, the first rake
length and the second rake length taken in a plane parallel to the
lower surface; wherein: the rake slant angle is equal to or greater
than 25.degree.; a rake extension ratio, defined as a ratio between
the first rake length and the second rake length, is smaller than 1
and equal to or greater than 0.8; and a major portion of each of
the curved cutting edges lies on a torus and extends along an angle
equal to or larger than 120.degree. as seen along the first axis of
symmetry.
Typically, the peripheral surface comprises a first pair of side
abutment surfaces that converge towards each other in a direction
toward the upper surface, and, a third pair of side abutment
surfaces that converge towards each other in a direction toward the
upper surface.
Still further in accordance with the present invention there is
provided a cutting tool having a longitudinal axis of rotation and
comprising: a tool body having at least one insert pocket formed in
a front end of the tool body and a cutting insert retained in the
at least one insert pocket, the at least one insert pocket
comprises: a pocket base abutment surface; a threaded bore
extending tangentially rearwardly from the pocket base abutment
surface; pocket side walls extending upwardly from the pocket base
abutment surface, two spaced apart of the pocket side walls are a
first pocket abutment surface, forming an acute first pocket
internal angle with the pocket base abutment surface, and a second
pocket abutment surface, forming an acute second pocket internal
angle with the pocket base abutment surface.
In one embodiment, the cutting tool's cutting insert comprises: two
opposing end surfaces and a peripheral surface extending
therebetween, each end surface having a mutual first axis of
symmetry passing through the end surfaces about which each end
surface has N-fold rotational symmetry, where N is a number from
the group consisting of 2, 3 and 4; a peripheral cutting edge
formed at the junction between each end surface and the peripheral
surface, the peripheral cutting edge comprising N curved cutting
edges (32, 34; 132, 134) merging with N straight cutting edges
which extend between the curved cutting edges at extremities
thereof; wherein the curved cutting edges of the two end surfaces
are not aligned, as seen in an end view of the cutting insert.
The cutting tool's cutting insert may further comprise: a first,
second, third and fourth pairs of side abutment surfaces, each pair
of the side abutment surfaces has 180.degree. rotational symmetry
around the through bore axis, the first pair of side abutment
surfaces converge towards each other in a direction toward the
upper surface, the second pair of side abutment surfaces converge
towards each other in a direction toward the lower surface, the
third pair of side abutment surfaces converge towards each other in
a direction toward the upper surface, the fourth pair of side
abutment surfaces converge towards each other in a direction toward
the lower surface, the third pair has 180.degree. rotational
symmetry with the fourth pair around a second symmetry axis that
passes between the third pair and the fourth pair, the upper
surface defines a first reference plane and the lower surface
defines a second reference plane, the first and second reference
planes are parallel to a median plane that is located midway
between the upper surface and the lower surface, the peripheral
surface forms with the first reference plane and with the second
reference plane an obtuse first internal included angle, as seen in
a first side view of the cutting insert that is perpendicular to a
given secondary cutting edge, the peripheral surface forms with the
first reference plane and with the second reference plane an acute
second internal included angle, as seen in a second side view of
the cutting insert that is perpendicular to the first side view,
the upper surface is provided with a planar upper central abutment
surface, constituting an insert upper base abutment surface, that
extends inwardly from an associated rake surface toward the through
bore; the lower surface is provided with a planar lower central
abutment surface, constituting an insert lower base abutment
surface, that extends inwardly from the associated rake surface
toward the through bore; wherein: in a retained position of the
cutting insert, the insert lower base abutment surface abuts the
pocket base abutment surface, one abutment surface of the insert
first pair of side abutment surfaces abuts the first pocket
abutment surface, one abutment surface of the insert third pair of
side abutment surfaces abuts the second pocket abutment surface,
and, a clamping screw passes through the through bore of the
cutting insert and threadingly engages the threaded bore of the
insert pocket.
In one embodiment, each side abutment surface of the first pair of
side abutment surfaces converges towards each other in a direction
toward the upper surface; each side abutment surface of the second
pair of side abutment surfaces converges towards each other in a
direction toward the lower surface; each side abutment surface of
the third pair of side abutment surfaces converges towards each
other in a direction toward the upper surface; and each side
abutment surface of the fourth pair of side abutment surfaces
converges towards each other in a direction toward the lower
surface.
If desired, the third pair of side abutment surfaces has
180.degree. rotational symmetry with the fourth pair of side
abutment surfaces around the symmetry axis.
Further if desired, the first pair of side abutment surfaces
converge towards each other in a direction toward the upper surface
as viewed in a cross-section taken in a first section plane, the
first section plane contains the through bore axis and is obliquely
disposed, as seen in an end view of the cutting insert, with
respect to a symmetry plane containing the through bore axis and
the symmetry axis.
Still further if desired, the second pair of side abutment surfaces
converge towards each other in a direction toward the lower surface
as viewed in a cross-section taken in a second section plane, the
second section plane contains the through bore axis and is
obliquely disposed at a plane angle, as seen in a top view of the
cutting insert, with respect to the symmetry plane and with respect
to the first section plane.
In one embodiment, the plane angle is 80.degree..
Typically, the peripheral surface forms with the first reference
plane and with the second reference plane an obtuse first internal
included angle, as seen in a first side view of the cutting insert
that is perpendicular to a secondary cutting edge; and the
peripheral surface forms with the first reference plane and with
the second reference plane an acute second internal included angle,
as seen in a second side view of the cutting insert that is
perpendicular to the first side view.
If desired, the first main cutting edge and the second main cutting
edge follow a major first radius of curvature along the major
portion thereof and a minor second radius of curvature along a
minor portion thereof.
Typically, the at least one insert pocket is provided with a pocket
abutment relief surface that is located above the second pocket
abutment surface, the pocket abutment relief surface being relieved
from the adjacent abutment surface of the insert fourth pair of
side abutment surfaces in a retained position of the cutting
insert.
In one embodiment, the cutting insert is four times indexable
within the at least one insert pocket.
Typically, the first pocket abutment surface forms with the second
pocket abutment surface an acute pocket angle as seen in a top view
of the at least one insert pocket.
If desired, the at least one insert pocket is provided with a
pocket relief channel located between the pocket side walls and the
pocket base abutment surface.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention and to show how
the same may be carried out in practice, reference will now be made
to the accompanying drawings, in which:
FIG. 1 is a perspective view of a cutting tool in accordance with
the present invention;
FIG. 2 is shows the cutting tool of FIG. 1 with a cutting insert in
accordance with the present invention removed from its pocket;
FIG. 3 is an enlarged perspective view of the cutting insert of
FIG. 2;
FIG. 4 is an end view of the cutting insert of FIG. 3;
FIG. 5 is an end view of the cutting insert of FIG. 3 showing the
cutting edges of both end surfaces without showing the through
bore;
FIG. 6 is a cross-sectional view of the cutting insert of FIG. 3
taken along line VI-VI in FIG. 7;
FIG. 7 is a first side view of the cutting insert of FIG. 3;
FIG. 8 is a second side view of the cutting insert of FIG. 3;
FIG. 9 is a cross-sectional view of the cutting insert of FIG. 3
taken along line IX-IX in FIG. 4;
FIG. 10 is a cross-sectional view of the cutting insert of FIG. 3
taken along line X-X in FIG. 4;
FIG. 11 is a top view of the insert pocket of FIG. 2;
FIG. 12 is a cross-sectional view of the insert pocket taken along
line XII-XII in FIG. 11;
FIG. 13 is a cross-sectional view of the insert pocket taken along
line XII-XII in FIG. 11 with the cutting insert retained in the
insert pocket by a clamping screw;
FIG. 14 is a top view of the cutting insert mounted in the insert
pocket and machining a workpiece;
FIG. 15 is a perspective view of another embodiment of the cutting
insert in accordance with the present invention;
FIG. 16 is a first side view of the cutting insert of FIG. 15;
FIG. 17 is a second side view of the cutting insert of FIG. 15;
FIG. 18 is a top view of the cutting insert of FIG. 15;
FIG. 19 is a cross-sectional view of the cutting insert of FIG. 15
taken along line XIX-XIX in FIG. 18;
FIG. 20 is a cross-sectional view of the cutting insert of FIG. 15
taken along line XX-XX in FIG. 18;
FIG. 21 is a cross-sectional view of the cutting insert of FIG. 15
taken along line XXI-XXI in FIG. 19; and
FIG. 22 is a cross-sectional view of another embodiment of the
cutting insert.
DETAILED DESCRIPTION OF THE INVENTION
Attention is first drawn to FIGS. 1 and 2 showing a cutting tool 10
in accordance with the present invention. The cutting tool 10 has a
longitudinal axis of rotation A defining a front-to-rear direction
of the cutting tool 10 and a direction of rotation R. The cutting
tool 10 comprises a tool body 12 having a plurality of insert
pockets 14 formed in a front end 16 of the tool body 12. A cutting
insert 18 is retained in each of the insert pockets 14 by means of
a clamping screw 20. The cutting insert 18 may be preferably made
from cemented carbide powders by pressing and sintering or by
injection molding techniques.
Attention is now drawn to FIGS. 3 to 10. The cutting insert 18
comprises an upper surface 22, defining a first reference plane P1,
a lower surface 24, defining a second reference plane P2, and a
peripheral surface 26 extending between the upper surface 22 and
the lower surface 24. The upper surface 22 and the lower surface 24
constitute end surfaces 28 of the cutting insert 18. In some
embodiments, the end surfaces 28 may be identical, and the first
reference plane P1 may be parallel to the second reference plane
P2.
The cutting insert 18 is provided with a through bore 30 having a
through bore axis B. The through bore 30 extends between the upper
surface 22 and the lower surface 24. In some embodiments, the
cutting insert 18 may have 180.degree. rotational symmetry around
the through bore axis B.
In some embodiments, each of the end surfaces 28 may comprise a
first main cutting edge 32 and a second main cutting edge 34. The
first main cutting edge 32 and the second main cutting edge 34 may
be identical. The cutting edges are formed at the junction between
each end surface 28 and the peripheral surface 26.
FIG. 5 is an end view of the cutting insert 18 showing the cutting
edges of both end surfaces without showing the through bore 30. The
cutting edges of the upper surface 22 are shown in solid lines and
the cutting edges of the lower surface 24 are shown in dashed
lines. As can be seen, the first and second main cutting edges 32,
34 of the upper surface 22 are angularly shifted with respect to
the first and second main cutting edges 32', 34' of the lower
surface 24. Thus, as seen in an end view of the cutting insert 18,
the main cutting edges of a given end surface 28 are not aligned
with the main cutting edges of the opposite end surface 28.
For sake of clarity, the non-alignment of the main cutting edges
may be described in the following manner. Each of the cutting edges
32, 34 has a cutting edge pivot axis C associated therewith. The
cutting edge pivot axis C is located in a mid portion 35 of the
cutting edge and extends parallel to an axis of symmetry S which
will be later described. The mid portion 35 refers to a region
including the geometrical center of the curved cutting edge and not
necessarily to the actual geometrical center of the curved cutting
edge.
Thus, as can be seen in FIG. 5, each of the curved cutting edges
32, 34 of one end surface 28 is rotated about its associated
cutting edge pivot axis C relative to the opposite curved cutting
edge 34', 32' of the other end surface 28. Thus, though the curved
cutting edges 32, 34 intersect cutting edges 34', 32',
respectively, when viewed along axis B, they clearly are not
aligned.
In an end view of the cutting insert 18, the first main cutting
edge 32 has a first radius of curvature R1 with respect to a first
cutting edge axis A1, and, the second main cutting edge 34 has a
second radius of curvature R2 with respect to a second cutting edge
axis A2. As shown in FIG. 5, the first cutting edge axis A1 and the
second cutting edge axis A2 may be parallel to the through bore
axis B and located at opposite sides thereof. As shown, the first
cutting edge axis A1 is located a first distance D1 from the second
main cutting edge 34, the through bore axis B is located a second
distance D2 from the second main cutting edge 34, and the first
distance D1 is smaller than the second distance D2.
Hence, as seen in an end view of the cutting insert 18, the first
cutting edge axis A1 is located closer to the second main cutting
edge 34 than the through bore axis B. In a similar manner, the
second cutting edge axis A2 is located closer to the first main
cutting edge 32 than the through bore axis B.
The first main cutting edge 32 and the second main cutting edge 34
do not have to follow a radius of curvature, and they may be curved
in other forms. For example, in one embodiment that is shown in
dashed lines in the upper portion of FIG. 5, the first main cutting
edge 32 and the second main cutting edge 34 may follow a major
first radius of curvature MR11 along a major angular portion MP11
thereof and a minor second radius of curvature MR21 along a minor
angular portion MP21 thereof.
In that embodiment, the major first radius of curvature MR11 may be
different than the minor second radius of curvature MR21.
Furthermore, the major first radius of curvature MR11 may extend
along a relatively large angle, represented by the major portion
MP11, for example, 120.degree., wherein the minor second radius of
curvature MR21 may extend along a smaller angle, represented by the
minor portion MP21, for example, 20.degree.. This embodiment is
shown with respect to only one main cutting edge, in this case,
with respect to the second main cutting edge. However, the
embodiment may be equally applicable to the first and second main
cutting edges.
In another embodiment that is shown in dashed lines in the lower
portion of FIG. 5, the major first radius of curvature MR12 may
extend along a relatively large angular portion MP12, for example,
140.degree., wherein the minor second radius of curvature MR22 may
extend along a much smaller angular portion MP22, for example,
1.degree. to 10.degree.. This embodiment is shown with respect to
only one main cutting edge, in this case, with respect to the first
main cutting edge. However, the embodiment may be equally
applicable to the first and second main cutting edges.
In other embodiments, the first main cutting edge 32 and the second
main cutting edge 34 are formed from several sections (not shown in
the figures) that have different radii of curvature and merge with
each other to form a continuously curved main cutting edge.
The first main cutting edge 32 has a leading end 36 and a trailing
end 38. The second main cutting edge 34 has a leading end 40 and a
trailing end 42. A first secondary cutting edge 44 merges, at a
leading end 46 thereof, with the leading end 36 of the first main
cutting edge 32, and, at a trailing end 48 thereof, with the
trailing end 42 of the second main cutting edge 34.
A second secondary cutting edge 50 merges, at a leading end 52
thereof, with the leading end 40 of the second main cutting edge
34, and, at a trailing end 54 thereof, with the trailing end 38 of
the first main cutting edge 32.
In one embodiment, the first secondary cutting edge 44 is identical
to the second secondary cutting edge 50. The first and second
secondary cutting edges 44, 50 are mainly used for performing
ramp-down operations and their length and shape are determined
according to machining needs. In one embodiment, the first
secondary cutting edge 44 and the second secondary cutting edge 50
are formed along straight lines.
As can be seen in FIG. 5, in addition to the fact that the first
and second main cutting edges 32, 34 of the upper surface 22 are
angularly shifted with respect to the respective second and first
main cutting edges 34', 32' of the lower surface 24, the first and
second secondary cutting edges 44, 50 of the upper surface 22 are
linearly shifted with respect to the first and second secondary
cutting edges 44', 50' of the lower surface 24.
The cutting insert 18 may have 180.degree. rotational symmetry
around a symmetry axis S. The symmetry axis S lies on a median
plane M between the first and second reference planes P1, P2, and
intersects the peripheral surface 26 at two median insert symmetry
points 56. Each of the median insert symmetry points 56 is formed
at the intersection of a first reference line L1 with a second
reference line L2, as seen in FIG. 7. FIG. 7 being a first side
view of the cutting insert 18 that is perpendicular to the first or
the second secondary cutting edges 44, 50.
In the embodiment described above, the main cutting edges 32, 34
are identical to each other, the secondary cutting edges 44, 50 are
identical to each other, and both end surfaces 28, namely, the
upper surface 22 and the lower surface 24 are identical to each
other. Therefore, for numbering the cutting edges of the lower
surface 24, an arbitrary decision was made to rotate the cutting
insert 18 180.degree. around the symmetry axis S. In this position,
the cutting edges which were previously located in the upper
surface 22 are now located in the lower surface 24 and a prime sign
was added to their number. Thus, for example, the corresponding
cutting edge of the first main cutting edge 32 is marked 32', and
so on.
The first reference line L1 connects the leading end 36 of a first
main cutting edge 32 of a given end surface 28 with the leading end
36' of a first main cutting edge 32' of the opposite end surface
28. The second reference line L2 connects the trailing end 42 of a
second main cutting edge 34 of a given end surface 28 with the
trailing end 42' of a second main cutting edge 34' of the opposite
end surface 28.
The peripheral surface 26 comprises a first pair of side abutment
surfaces 58, a second pair of side abutment surfaces 60, a third
pair of side abutment surfaces 62 and a fourth pair of side
abutment surfaces 64. In one embodiment, each pair of the side
abutment surfaces 58, 60, 62, 64 has 180.degree. rotational
symmetry around the through bore axis B.
As seen in FIG. 9, each side abutment surface of the first pair of
side abutment surfaces 58 converges towards each other in a
direction toward the upper surface 22. FIG. 9 is a view of a
cross-section taken in a first section plane P3. As seen in the end
view of FIG. 4, the first section plane P3 contains the through
bore axis B and is obliquely disposed with respect to a symmetry
plane SP containing the through bore axis B and the symmetry axis
S.
As seen in FIG. 10, each side abutment surface of the second pair
of side abutment surfaces 60 converges towards each other in a
direction toward the lower surface 24. FIG. 10 is a view of a
cross-section taken in a second section plane P4. The second
section plane P4 contains the through bore axis B and is obliquely
disposed, as seen in FIG. 4, with respect to the symmetry plane SP
and with respect to the first section plane P3. In one embodiment,
the first section plane P3 forms with the second section plane P4 a
plane angle .phi. of 80.degree., with a supplementary angle of
100.degree..
The plane angle .phi. between the first section plane P3 and the
second section plane P4 may be seen also in FIG. 6, where the first
section plane P3 is perpendicular to the first pair of side
abutment surfaces 58 and the second section plane P4 is
perpendicular to the second pair of side abutment surfaces 60. Both
first section plane P3 and second section plane P4 are
perpendicular to the median plane M, which also contains the
symmetry axis S.
As seen in FIG. 8, each side abutment surface of the third pair of
side abutment surfaces 62 converges towards each other in a
direction toward the median plane M. Similarly, each side abutment
surface of the fourth pair of side abutment surfaces 64 also
converges towards each other in a direction toward the median plane
M. One may likewise consider the third pair of side abutment
surfaces 62 to converge towards each other in a direction toward
the upper surface 22, and the fourth pair of side abutment surfaces
64 to converge towards each other in a direction toward the lower
surface 24.
In one embodiment, the third pair of side abutment surfaces 62 has
180.degree. rotational symmetry with the fourth pair of side
abutment surfaces 64 around the symmetry axis S.
As seen in FIG. 7, the peripheral surface 26 forms with the first
reference plane P1 and with the second reference plane P2 an obtuse
first internal included angle .alpha.. FIG. 7, being a first side
view of the cutting insert 18, is viewed from a direction
perpendicular to a secondary cutting edge 44.
FIG. 8 is a second side view of the cutting insert 18 taken in a
direction perpendicular to the symmetry plane SP. The direction
perpendicular to the symmetry plane SP is represented by an
imaginary plane N. Hence, the direction of the second side view of
the cutting insert 18 is perpendicular to the direction of the
first side view of the cutting insert 18. As seen in FIG. 8, the
peripheral surface 26 forms with the first reference plane P1 and
with the second reference plane P2 an acute second internal
included angle .beta..
As can be seen in FIG. 5, the first cutting edge axis A1 and the
second cutting edge axis A2 are located at opposite sides of the
symmetry plane SP. The first cutting edge axis A1 is distanced a
first axis distance D5 from the symmetry plane SP and the second
cutting edge axis A2 is distanced a second axis distance D6 from
the symmetry plane SP. According to one embodiment, the first axis
distance D5 is equal to the second axis distance D6.
In one embodiment, as can be seen in FIG. 5, the first cutting edge
axis A1 and the second cutting edge axis A2 may be located at
opposite sides of the imaginary plane N. In that case, the first
cutting edge axis A1 is distanced a third axis distance D7 from the
imaginary plane N and the second cutting edge axis A2 is distanced
a fourth axis distance D8 from the imaginary plane N. According to
one embodiment, the third axis distance D7 is equal to the fourth
axis distance D8.
As can be best seen in FIGS. 3 and 4, the first and second main
cutting edges 32, 34 of a given end surface 28 and their associated
first and second secondary cutting edges 44, 50 form a continuously
extending cutting edge 66 that is associated with a rake surface
68. In one embodiment, the rake surface 68 extends continuously
along the entire length of the cutting edge 66. The rake surface 68
extends inwardly from the cutting edge 66 toward the through bore
axis B, and slopes rearwardly toward the median plane M in the
direction of the other end surface 28.
The upper surface 22 of the cutting insert 18 is provided with a
planar upper central abutment surface 70 that extends inwardly from
the associated rake surface 68 toward the through bore 30.
Similarly, the lower surface 24 is provided with a planar lower
central abutment surface 72 that extends inwardly from the
associated rake surface 68 toward the through bore 30.
As seen in FIG. 9, the upper central abutment surface 70 is
distanced a third distance D3 from the lower central abutment
surface 72, the first reference plane P1 is distanced a fourth
distance D4 from the second reference plane P2, and, the third
distance D3 is smaller than the fourth distance D4. Thus, the
central abutment surfaces 70, 72 are recessed toward the median
plane M, relative to their respective associated reference planes
P1, P2.
Attention is now drawn to FIGS. 11 to 14. Each insert pocket 14
comprises a pocket base abutment surface 74. The pocket base
abutment surface 74 may be planar, and it may be formed as a single
surface, as shown in FIG. 11, or be divided into several surfaces.
If the pocket base abutment surface is divided into several
surfaces, the several surfaces may be separated by relief grooves.
A threaded bore 76 extends tangentially rearwardly from the pocket
base abutment surface 74.
The insert pocket 14 further comprises pocket side walls 78 that
extend upwardly from the pocket base abutment surface 74. Two of
the pocket side walls 78 form pocket abutment surfaces. In one
embodiment, the pocket abutment surfaces are spaced apart by a
pocket side wall 78 that does not form a pocket abutment
surface.
The pocket abutment surfaces comprise a first pocket abutment
surface 80 and a second pocket abutment surface 82. The first
pocket abutment surface 80 forms an acute first pocket internal
angle .gamma. with the pocket base abutment surface 74, and the
second pocket abutment surface 82 forms an acute second pocket
internal angle .delta. with the pocket base abutment surface
74.
In a retained position of the cutting insert 18, the insert lower
central abutment surface 72 abuts the pocket base abutment surface
74, one abutment surface of the insert first pair of side abutment
surfaces 58 abuts the first pocket abutment surface 80, one
abutment surface of the insert third pair of side abutment surfaces
62 abuts the second pocket abutment surface 82, and, the clamping
screw 20 passes through the through bore 30 of the cutting insert
18 and threadingly engages the threaded bore 76 of the insert
pocket 14.
By means of the acute internal angles .gamma. and .delta., the
seating of the insert first 58 and third 62 operative side abutment
surfaces against the first and second pocket abutment surfaces 80,
82 provides a firm clamping of the cutting insert 18 in a dove-tail
manner thus better securing the cutting insert 18 within the insert
pocket 14.
The insert pocket 14 is provided with a pocket abutment relief
surface 84 that is located above the second pocket abutment surface
82 and away from the pocket base abutment surface 74. In a retained
position of the cutting insert 18, the pocket abutment relief
surface 84 is relieved from the adjacent abutment surface of the
insert fourth pair of side abutment surfaces 64.
The insert pocket 14 is further provided with a pocket relief
channel 86. The pocket relief channel 86 is located between the
pocket side walls 78 and the pocket base abutment surface 74. When
the cutting insert 18 is retained within the insert pocket 14, the
pocket relief channel 86 provides adequate clearance to the cutting
edge 66 associated with the lower central abutment surface 72 of
the cutting insert 18 that abuts the pocket base abutment surface
74.
As can be best seen in FIG. 11, the first pocket abutment surface
80 forms with the second pocket abutment surface 82 an acute pocket
angle .theta. in order to adequately support the side abutment
surfaces of the cutting insert 18.
FIG. 14 shows a top view of the cutting insert 18 when retained
within an insert pocket 14 and machining a workpiece W. For sake of
clarity, only a part of the tool body 12 is shown. As shown, the
active main cutting edge 32 that may be round along a relatively
large arc enables the cutting tool 10 to effectively machine, for
example, internal profiles of turbine blades T along the entire
internal surface 88 of the blade T.
The cutting insert 18 drawn in solid lines shows the location of
the cutting insert when beginning to machine the internal surface
88 of the turbine blade T. The cutting insert 18 drawn in dashed
lines shows the location of the cutting insert when ending the
machining of the internal surface 88 of the turbine blade T.
As can be seen by the two extreme positions of the cutting insert
18 with respect to the internal surface 88 of the turbine blade T,
the entire active main cutting edge 32 is operative during this
machining process. Since the main cutting edge 32 extends along a
relatively large arc, it is effective for machining an entire
concave internal surface 88 of a turbine blade T.
In other applications (not shown), the active secondary cutting
edge 44 may effectively perform ramp-down operations.
Hence, as described above, according to one embodiment of the
present invention, the cutting insert 18 is capable of performing a
variety of cutting operations, and may be four times indexable
within an insert pocket 14.
Attention is now drawn to FIGS. 15 to 21 which show another
embodiment of the cutting insert. In these figures, like parts are
designated with like reference numerals with the addition of 100.
The cutting insert 118 shown in FIGS. 15 to 21 has a structure
similar to the structure of the cutting insert 18 described above,
however, it differs in the shape of its cutting edges.
The cutting insert 118 comprises, in each end surface 128 thereof,
first and second main cutting edges 132, 134 that are connected,
through extremities thereof, to first and second secondary cutting
edges 144, 150.
The first main cutting edge 132 has a leading end 136 and a
trailing end 138. The second main cutting edge 134 has a leading
end 140 and a trailing end 142. A first secondary cutting edge 144
merges, at a leading end 146 thereof, with the leading end 136 of
the first main cutting edge 132, and, at a trailing end 148
thereof, with the trailing end 142 of the second main cutting edge
134.
A second secondary cutting edge 150 merges, at a leading end 152
thereof, with the leading end 140 of the second main cutting edge
134, and, at a trailing end 154 thereof, with the trailing end 138
of the first main cutting edge 132.
In one embodiment, the first secondary cutting edge 144 may be
identical to the second secondary cutting edge 150. The first and
second secondary cutting edges 144, 150 are mainly used for
performing ramp-down operations and their length and shape are
determined according to machining needs. In one embodiment, the
first main cutting edge 132 may be identical to the second main
cutting edge 134.
As can be clearly seen in the figures, the leading end 136 of the
first main cutting edge 132 is located further from the median
plane M than the trailing end 138 of the first main cutting edge.
Similarly, the leading end 140 of the second main cutting edge 134
is located further from the median plane M than the trailing end
142 of the second main cutting edge 134. Such a construction of the
first and second main cutting edges 132, 134 provides the cutting
insert 118 a highly positive rake with respect to the upper central
abutment surface 170.
Each of the first and second main cutting edges 132, 134 lies on a
torus. Furthermore, when the cutting insert is retained in the
insert pocket 14 of the cutting tool 10, and the cutting tool is
rotated about its axis of rotation A by 360.degree., each point on
an operative main cutting edge, i.e., first main cutting edge 132
or second main cutting edge 134, sweeps out a portion of a
torus.
The first and second main cutting edges 132, 134 and their
associated first and second secondary cutting edges 144, 150 form a
continuously extending cutting edge 166 that is associated with a
rake surface 168 that may extend continuously along the entire
circumference of an end surface 128. As shown in FIGS. 18 to 21,
the rake surface 168 merges with the upper central abutment surface
170 through an undercut 90 which serves two purposes. First, it
enables better control of the chips produced during machining.
Second, it enables better distinguishing of the upper central
abutment surface 170 with respect to the upper surface 122 of the
cutting insert 118, thus assuring satisfactory abutment properties
of the upper central abutment surface 170. As can be seen in FIGS.
19 to 21, the undercut 90 may vary in size and shape at different
cross-sections of the cutting insert 118. Similarly, the same may
be applied to the lower surface 124 of the cutting insert 118.
In the embodiments described above, the height orientation of the
main cutting edges 132, 134 with respect to the central abutment
surface 170 is such that the cutting edges are higher than the
central abutment surface, i.e., the central abutment surface 170 is
located closer to the median plane M than the main cutting edges
132, 134. However, in other embodiments (not shown) the main
cutting edges 132, 134, or at least a portion thereof, may be
located closer to the median plane M than the central abutment
surface 170.
The construction of the cutting insert 118 enables considerable
advantages during machining, as can be appreciated by a person
skilled in the art. The highly positive rake of the main cutting
edges provides the operative main cutting edge of the cutting
insert 118, when the cutting insert 118 is mounted in the cutting
tool 10 during machining, with a less negative rake angle, compared
to the negative rake angle of the cutting insert 18 shown in FIG. 1
that is mounted in a negative axial positioning. The less negative
axial rake leads to easier cutting, better chip removal, lower
cutting forces, and, lower power consumption. This construction of
the cutting insert 118 may be used when it is required to machine
relatively high tensile materials and high temperature alloys. A
further advantage in this case may be avoiding adhesion of the
chips.
Attention is now drawn to FIG. 22 which shows another embodiment of
the cutting insert. In this figure, like parts are designated with
like reference numerals with the addition of 200.
As shown, a cutting insert 218 comprises two end surfaces 228 and a
peripheral surface 226 extending therebetween. One of the end
surfaces 228 forms an upper surface 222 similar to the upper
surface 122 of the cutting insert 118 described above, and, another
end surface forms a lower surface 224 of the cutting insert 218.
The upper surface 222 comprises a continuously extending peripheral
cutting edge 266 associated with a continuously extending rake
surface 268.
The peripheral cutting edge 266 comprises two curved cutting edges,
namely, a first main cutting edge 232 and a second main cutting
edge 234, and, two straight cutting edges, namely, a first
secondary cutting edge and a second secondary cutting edge 250
connecting between extremities of the first and second main cutting
edges 232, 234 (the first secondary cutting edge is not shown).
In order to better cut ductile materials, the rake surface 268 is
formed considerably larger than the rake surface 168 of the cutting
insert 118. The rake surface 268 is slanted at a rake slant angle
.lamda. with respect to the lower surface 224 of the cutting insert
218. The rake slant angle .lamda. is relatively large and is
preferably equal to or greater than 25.degree..
A rake inner extremity 92 is defined at a region where an innermost
extremity of the rake surface 268 merges with a bore peripheral
region 94 that surrounds the through bore 30. The bore peripheral
region 94 merges with the through bore 30 at a bore upper end 96
and it extends generally parallel to the lower surface 224 of the
cutting insert 218. A first rake length H1 is defined between a
given point 98 on the peripheral cutting edge 266 and the rake
inner extremity 92, measured in a plane parallel to the lower
surface 224. A second rake length H2 is defined between the same
given point 98 on the peripheral cutting edge 266 and the bore
upper end 96, measured in a plane parallel to the lower surface
224.
A rake extension ratio E is defined as a ratio between the first
rake length H1 and the second rake length H2. The rake extension
ratio E may vary within a preferable range. According to one
embodiment, the rake extension ratio E is smaller than b 1 and
equal to or greater than 0.8.
Since the rake surface 268 is relatively very large, it extends, in
an inward direction of the cutting insert 218, almost to the
through bore 30. With such a construction, the upper surface 222
lacks a central abutment surface, in contrary to the existence of
the central abutment surface 170 in the upper surface 122 of the
cutting insert 118.
Thus, since the cutting insert 218 lacks a central abutment
surface, it cannot be used as a double sided cutting insert.
Therefore, the lower surface 224 of the cutting insert 118 lacks
cutting edges, and is formed flat in order to serve solely as an
abutment surface. Accordingly, the peripheral surface 226 is formed
only with the abutment surfaces required for abutment of a single
sided cutting insert, namely, the first pair of side abutment
surfaces 258, and, the third pair of side abutment surfaces 262
(not shown).
Although the present invention has been described to a certain
degree of particularity, it should be understood that various
alterations and modifications could be made without departing from
the spirit or scope of the invention as hereinafter claimed.
The cutting insert is not limited to have two main cutting edges on
each end surface. In one embodiment (not shown), the cutting insert
is provided with three main cutting edges which are connected, at
extremities thereof, by three secondary cutting edges. The three
main cutting edges may be identical. Likewise, the three secondary
cutting edges may be identical.
In one embodiment (not shown), the cutting insert is provided with
four main cutting edges which are connected, at extremities
thereof, by four secondary cutting edges. The four main cutting
edges may be identical. Likewise, the four secondary cutting edges
may be identical.
Thus, a cutting insert according to the present invention may be
retained by a clamping screw passing through a through bore. The
cutting insert may have four, six or eight rounded cutting edges,
wherein the cutting insert may be indexed four, six or eight times.
The cutting edges may extend along a large arc and may extend at an
angle larger than 120.degree..
* * * * *